Phytoparasitic nematodes cause severe damage and yield losses to numerous agricultural crops. Considering the revision of the EU legislation on the use of pesticides on agricultural crops, control strategies with low environmental impact are required. The approach based on the use of bacteria seems particularly promising as it also helps to reduce the applied amounts of chemicals and stabilize ecological changes. This paper gives an overview of the main types of bacteria that can be used as biological control agents against plant parasitic nematodes and their interrelationships with plants and other organisms. Many experiments have given positive results of phytoparasitic nematode control by bacteria, showing possible prospects for their application. In vitro, greenhouse and field experiments have shown that bacteria can regulate the development of ecto- and endoparasitic nematodes by different modes of action. Triggering the induction of plant defense mechanisms by bacteria is seen as the optimum tool because the efficacy of bacterial treatment can be higher than that of chemical pesticides or at least close to it. Moreover, bacterial application produces additional positive effects on growth stimulation, raises yields and suppresses other pathogenic microorganisms. Commercial formulations, both as single bacterial strains and bacterial complexes, are examined.

Root-knot disease caused by Meloidogyne incognita leads to significant crop yield losses that may be aggravated by the association with pathogenic fungi and bacteria. Biological agents can be effectively used against the complex disease of root-knot nematode and pathogenic fungi. In this study, 35 bacterial strains were analyzed for their in vitro nematicidal, antagonistic and growth stimulation activities. Based on results from the in vitro assays, grow-box experiments on tomato and cucumber were carried out with the strain BZR 86 of Bacillus velezensis applied at different concentrations. Effects of B. velezensis BZR 86 on the development of root-knot disease were evaluated by recording root gall index, number of galls and number of eggs in egg masses. Application of B. velezensis BZR 86 noticeably decreased the development of root-knot disease on tomato and cucumber plants, as well as significantly increased growth and biomass of cucumber plants in accordance with bacterial concentration. This study seems to demonstrate that strain B. velezensis BZR 86 could be an additional tool for an environmentally safe control of root-knot disease on horticultural crops.

The structure of the microbial biomass and trophic nematode groups were studied in soddy-podzolic soils under phytocenoses of a secondary succession initiated by the growth of forests on agricultural lands in the southern taiga. The microbial biomass became greater with the increasing amount of fungal mycelium, and the bacterial pool little changed in these soils. Bacteriovorous nematodes predominated (64% of the total number of nematodes) in the soils of a potato field, where the bacterial biomass was maximal; it was greater or close to the fungal biomass. In the soil under a mown meadow, where the fungal biomass was greater, the populations of fungivorous and bacteriovorous nematodes were close in number and share in the nematode complex (by 40%). In the soil under a spruce forest (climax stage), the main biomass pool was composed of fungi (97%), whose biomass is maximal, while fungivorous nematodes and nematodes with a mixed type of feeding occupy the dominant positions (69% in the nematode complex). In the course of the succession, the number of fungivorous and bacteriovorous nematodes decreased, but their ratio increased from 0.4 in the soil of the potato field to 0.8–1.0 under the meadows and mixed forest and to 2.0 in the soil under the sorrel spruce forest. These changes corresponded to the increasing microbial pool and the share of the fungal biomass in it.

The soil nematode communities in typical tundra soils of southern Chukotka have been analyzed. Five types of shrub and grass-shrub biotopes on Cryosols, Fluvisols, Histosols, Gleysols, and Cambisols were examined. The animals were extracted from the soil by the Baermann technique with subsequent determination of taxonomic diversity, total and relative abundance, and trophic groups. The highest number (7044 individuals/100 g of soil) and biomass (12.15 mg) of nematodes were found in the Histosol, and the minimum one (1000 individuals/100 g of soil; 1.96 mg) of nematodes in the Cryosol. Bacterivorous nematodes dominated in all soil types. The maximum percentage of bacterivorous nematodes (94%) were found in the Cambisol. The percentages of fungivorous nematodes in the studied soils ranged from 1 to 42%. Predatory and omnivorous nematodes were present in all soils except for the litter of the Cambisol. Their percentage ranged from 2 to 32%. Phytonematodes were few, their highest number was found in the Gleysol (18%). The nematode fauna of the soils under analysis differed significantly. The greatest diversity of nematodes was found in the peat horizon of the Fluvisol, and the smallest diversity of nematodes was recorded in the litter of the Cambisol. The values of Sigma Maturity Index ranged between 2 and 3. The Enrichment Index had low and moderate (1.40–41.02) values, and the Structure Index had high values (59.51–84.07). The Eudorylaimus and Plectus genera were eudominants in all soil types. The soil food webs formed in the biocenoses under consideration can be characterized as stable and structured except for the alder biocenosis.

Nematode complexes of the forest soils of Bale National Park in Ethiopia (southern macroslope) have been investigated at the end of wet season. The nematodes of Nitisols and Acrisols formed in Hagenia and Hagenia-Juniperus forests, and suspended soils formed in Hagenia abyssinica canopy have been compared. The nematodes were extracted by the Baermann technique with subsequent determination of total numbers, taxonomic diversity, and trophic groups. The status of ecosystems was determined using ecological indices. The number of nematodes in suspended soils was several times higher than in forest soils, with the biomass of animals ten times greater. The bacterivorous nematodes prevailed in all soils; in the suspended soil their percentage was 75%. The plant parasites and fungivorous nematodes were few in suspended soil compared to Acrisols and Nitisols. In the suspended soils that were less diverse and structural, the fast-reproducing genera-colonizers prevailed. Acrobeloides, Plectus and Rhabditis were eudominants in the suspended soils, whereas Panagrolaimus, Helicotylenchus, and Mesodorylaimus predominated in Nitisols. The trophic webs of all three soil types were mature, stable, with low level of disturbance.